Question about how to charge a AGM battery.

Hello all,

Since my current battery is dead (drops from full charge state in one night to 11.8v) i have got myself a replacement. A Yuasa YTX12-BS.

If i googled right, this battery is a AGM battery, and if i search how to charge them i do not get a clear answer, so maybe you can help me out.

This YTX12-BS is a 10ah battery.
On a dutch battery forum (where there is only a few topics on the entire forum?) is a FAQ and stating that every lead acid battery should be charged minimum with 10% of current of his capacity. Example: 55ah battery should be charged with a 5.5a/hr current and a 110ah battery with 11a/hr etc.

So the YTX12-BS is a 10ah, so the minimum current should be 1a/hr ?
Then there is the discussions about AGM.

Normal non-AGM lead acid batteries should be charged with a maximum of 14.4 volts to prevent them from being boiled. The internal structure in AGM battery is different: using calcium plates with glass fiber mats and not 100% lead and therefor should be charged with a slightly higher voltage> 14.7v.

Now is the question..
Can i do this ? or do i damage my brand new battery ?
The charger i got is a Oxford Maximizer 360T.
According to the specifications it has 3 options:
-1 Motorcycle, 0.6a/hr. 14.4v
-2 Car battery, 3.6a/hr. 14.4v
-3 AGM battery, 3.6a/hr. 14.7v

If i take the minimum amps current into account, the minimum charging for this battery is 1amps/hour. On the motorcycle mode it only charges 0.6amps and if i understood correctly, this could give problems because of the internal resistance of the battery and also the charger. On the battery is stating normal charge 2a and quick charge 5a. So it is capable of handling the 3.6a current that the oxford charger also can provide..

So i hope you guys have more experiencing in charging AGM batteries.
I simply do not want to overcharge the battery, but i on CTEK website (manufacture of chargers) i read that they NEED a slightly higher voltage to charge AGM batteries.. but i simply do not want to destroy my new battery.. (70 euros!)

[tigersaw]

I should not worry about it too much. After all, the day to day charging from the bike isn't regulated to any such degree.
General rule of thumb for charging batteries is 10% of rated capacity for 14 hours. Stick to that and you wont go far wrong. Looking at your options, I'd go for 0.6 AH, you wont damage anything by undercharging, then stick it on the bike.

There you have a point..
According to the service manual the charging voltage at 5000rpm is between 14.0 and 15.5 volts..

This is what i get at the CTEK (manufacture of chargers)
"AGM, Absorbed Glass Mat,keeps the acid in place by the separator paper that consists of a fibreglass mat operating like a sponge. The capillary forces in the separator do the trick. The batteries can be constructed with extremely thin separators which keep the internal resistance low. This means that you can leverage high power from a small volume which makes it ideal as a starter battery. AGM has one drawback which is that the amount of acid is limited. All acid must be absorbed by the separator paper and when the small amount of acid has been converted into lead sulphate, this signals that the "petrol tank" is empty. To deal with this problem, AGM batteries often have a somewhat higher acid weight. This means that an AGM battery can, and often should, be charged using a voltage that is a little higher. VRLA batteries are very sensitive to "unclean current", i.e. high current ripple, see link. For this reason, traditional transformer battery chargers should not be used.

[Sid Squid]

Put in the charger you have - it will be fine.